Cascade PID-Lead Compensator Controller for Non-overshoot Time Responses of unstable system

In process control industries, one of the major and serious problems is presence of overshoot on controlled variables. This paper deals with the elimination overshoot in step response by using conventional PID controller with cascading of lead compensator. The proposed cascade technique consists of inner loop with lead compensators and outer loop with PID controller. The processes industry consists of many control loops and most of the control loops are consists of PI and PID controller. The PI/PID controller is used in the control loop with unstable system, the time response is oscillatory due to gain margin and phase margin. The proposed idea is to use the cascade control principle to control the unstable system with cascaded PID and Lead compensator. The compensator is used to compensate desired phase margin value of system and then make use of the PID controller is to control the system with robust, reduced order response, and thus, suppressing the overshoot in time response. The validity of the proposed approach is verified through simulation for the level control of unstable biochemical reactor.